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• The evolution of performances of the waste management system is described. • Plenty of detailed data on waste collection over 30 years are presented. • Material flows have been tracked: 72 waste treatment facilities were identified. • Criticalities of material recovery indices are highlighted through examples. • The case study may represent a model for other realities. The Circular Economy model is gaining attention as a key factor for boosting sustainable development. Reducing the consumption of raw materials, as well as increasing the amount of recycled waste, are the current challenges the municipal solid waste management system is called for. In this study, the evolution of the municipal waste management strategies in the city of Brescia was analysed, covering a period of 30 years. The results obtained by a) progressively extending the separate collection with street containers, b) building a Waste to Energy plant, and c) moving to a door to door collection system, were assessed via numerical indicators and mass balances. In order to highlight the complexity of the system, the waste flow, from collection to the achievement of the "end of waste" attribute, was followed. Separate collection with street containers came to a saturation percentage around 40%. The realization of the incineration plant eliminated the direct disposal of waste to landfills. With the introduction of the new collection system, the separately collected waste increased up to over 73%, the per capita amount of collected waste decreased from 685.3 kg/(in y) to 579.6 kg/(in y), and a significant reduction of recyclable materials in the unsorted waste was gained. In the paper, these achievements and their affecting factors are analysed. Moreover, criticalities in the calculation of material recovery indices due to the complexity of the system (72 transformation sites were identified) are discussed. [ABSTRACT FROM AUTHOR]

Abstract This opinion paper focuses on the role of eco-toxicological tools in the assessment of possible impacts of emerging contaminants on the aquatic ecosystem, hence, on human health. Indeed, organic trace pollutants present in raw and treated wastewater are the pivot targets: a multidisciplinary approach allows defining the basic principles for managing this issue, from setting a proper monitoring campaign up to evaluating the optimal process treatment. Giving hints on trace pollutants fate and behaviour, attention is focused on the choice of the bioassay(s), by analysing the meaning of possible biological answers. Data interpretation and exploitation are detailed with the final goal of providing criteria in order to be able to select the best targeted treatment options. The manuscript deals with conventional and innovative analytical approaches for assessing toxicity, by reviewing laboratory and field assays; illustrative real scale and laboratory applications integrate and exemplify the proposed approach. Graphical abstract Unlabelled Image Highlights • Bioassays must be chosen by taking into account the meaning of biological responses. • Lab and in situ bioassays must be integrated, based on reliability and applicability. • Trace pollutants can cause unpredictable and non-linear biological responses. • Wastewater composition and flowrate variability affects any toxicity assessment. • Environmental and socio-economic aspects underpin sewage treatment scheme choice. [ABSTRACT FROM AUTHOR]

The wastewater treatment process is based on complex chemical, physical and biological mechanisms that are closely interconnected. The efficiency of the system (which depends on compliance with national regulations on wastewater quality) can be achieved through the use of tools such as monitoring, that is the detection of parameters that allow the continuous interpretation of the current situation, and experimental tests, which allow the measurement of real performance (of a sector, a single treatment or equipment) and comparison with the following ones. Experimental tests have a particular relevance in the case of municipal wastewater treatment plants fed with a strong industrial component and especially in the case of plants authorized to treat aqueous waste. In this paper a case study is presented where the application of management tools such as careful monitoring and experimental tests led to the technical and economic optimization of the plant: the main results obtained were the reduction of sludge production (from 4,000 t/year w.w. (wet weight) to about 2,200 t/year w.w.) and operating costs (e.g. from 600,000 €/year down to about 350,000 €/year for reagents), the increase of resource recovery and the improvement of the overall process performance. [ABSTRACT FROM AUTHOR]

Wastewater treatment facilities are increasingly being considered as centralized installations where various resources can be recovered from the sewage. Novel technological solutions are already available for achieving this goal. However, their application to upgrade existing plants can be far more challenging than building new dedicated plants. While the scientific literature is generally focused on testing and comparing the recovery options, this work was aimed at giving a holistic evaluation of the actual impacts of upgrading existing facilities. Commercially available systems were considered for retrofitting two plants of different size (50,000 and 500,000 population equivalents) and achieving either energy self-sufficiency or material recovery. Based on mass and energy balances, a detailed evaluation of technical, social, economic, and administrative aspects was carried out. Environmental aspects were also included, adopting a simplified approach. It turned out that energy self-sufficiency (external energy supply reduced down to about 10% of the total need) is not far away to be achieved, with moderate techno-economic implications, especially when the plant is already equipped with primary sedimentation and anaerobic digestion. Integral recovery of treated effluent, sludge and nitrogen can also be pursued in large facilities, while several potential criticalities arise for medium-sized plants. The adopted procedure evidenced critical aspects that are often disregarded in the decision process: this may suggest where to address efforts in evaluating real situations. [ABSTRACT FROM AUTHOR]

Wet Oxidation (WO) models are generally employed for reactor design, thus WO modeling is a topic of great interest. Indeed, WO is one of the different technologies studied for sludge minimization and treatment, which represent crucial aspects in the management of wastewater treatment plants (WWTP). Different Generalized Lumped Kinetic Models (GLKM) for sewage sludge WO were proposed in the literature for describing the complex transformations occurring in the process. Usually, works are related to a single type of sludge and, consequently, kinetic constants cannot be used for different case studies. In the present paper an alternative approach has been followed. A mathematical model was proposed and identified on a set of six different types of sludge (primary, secondary and mixed sludge from both urban and industrial WWTP). Kinetic parameters were determined for the different types of sludge with the non-linear least-squares method. In general, the predicted COD values obtained with the estimated kinetic constants closely fit experimental data: the mean absolute error associated with total (dissolved) COD is 3.2% (3.7%) and 10% (17%), respectively for the best and worst case. Kinetic constants values were finally correlated to the sludge VSS/TSS ratio (VSS = Volatile Suspended Solids; TSS = Total Suspended Solids) in order to provide a tool for a gross estimation of WO kinetic parameters, for a given sludge, relying on simple analytical measurement (VSS and TSS), commonly available at every WWTP. [ABSTRACT FROM AUTHOR]

Sewage sludge processing is a key issue in water resource recovery facilities due to the inefficacy of conventional treatments to produce high quality biosolids to be safely used in agriculture. Under this framework, the performances of several enhanced stabilization processes, namely ultrasound-pretreated Mesophilic Anaerobic Digestion (US+MAD), thermophilic anaerobic digestion (TAD), thermal-pretreated TAD (TH+TAD) and ultrasound-pretreated inverse Temperature Phased Anaerobic Digestion (US+iTPAD) have been investigated. Such enhanced processes resulted in higher biogas yields and higher destruction of pathogens with respect to conventional MAD process, thus suggesting their feasibility in full-scale implementation perspectives. A procedure for technical-economic comparison of new sludge processing lines against conventional ones (benchmarking) was developed, based on the definition of technical issues (e.g. reliability, complexity, etc.) which are rated for each situation. Moreover, capital and operating costs were estimated. The enhanced processes analyzed in this work showed some potentially critical items, mainly related to energy balance and reagent consumption. Water Environ. Res., 88, 468 (2016). [ABSTRACT FROM AUTHOR]

In this work we have performed a feasibility study of two upgrading alternatives for sewage sludge stabilization aimed to the reduction of the produced sludge and to the improvement of its qualitative characteristics with respect to its final destination: agricultural use or incineration. The first upgrading (1) proposes the separated thickening: primary sludge is thickened by gravity while dynamic thickening is applied to secondary sludge. The second upgrading (2) introduces a post-aerobic digestion stage (after the anaerobic one), in addition to separate thickening. Technical-economic and environmental assessments have been performed in comparison to a conventional wastewater treatment plant, which operates with gravity thickening and anaerobic digestion of mixed sludge. In the post-aerobic stage, operated with intermittent aeration, additional volatile solids removal of 45% and nitrification and denitrification efficiencies of 97% and 70%, respectively, were achieved. Both upgrading alternatives gained a positive technical evaluation with the only exceptions of the item “ Thermal energy consumption ” in upgrading 1 for agricultural reuse, and, to a minor extent, the “ Energy available for external recovery ” for incineration in both upgrading options. Cost analysis showed that the two upgrading alternatives are generally cheaper than the conventional plant, even if the results are dependent on local conditions, which have to be considered. Results of the environmental assessment showed that the upgrades with incineration perform better than the reference for all impact categories except freshwater eutrophication, with upgrading 2 as the best option. For the agricultural use, different results were obtained for the different impact categories with critical aspects mainly related to phosphorus and ammonia emissions for upgrading 1. [ABSTRACT FROM AUTHOR]

Nowadays, several technologies and management strategies are proposed for upgrading wastewater treatment plants (WWTPs) in order to improve sludge stabilization or minimize sludge production. In order to make sure that this leads to overall improvements, their techno-economic and environmental performance has to be carefully evaluated. In response to this, the techno-economic and environmental performance was assessed for a considered model reference WWTP upgraded with separate treatment and disposal for primary and secondary sludge to provide guidance to research, policy and investment efforts. This paper departs in an experimental campaign carried out within the EU project “ROUTES” and describes an assessment of an upgrade of a WWTP, involving wet oxidation of primary sludge and thermophilic anaerobic digestion (integrated with thermal hydrolysis pre-treatment) for secondary sludge. The reference plant and the upgrade implied different disposal routes for the resulting sludges: incineration for the stabilized sludge deriving from the reference WWTP; agricultural land application for the secondary stabilized sludge from the upgraded plant and landfilling for the solid residue deriving from the wet oxidation process (as non-hazardous waste). The mass balance carried out for both reference and upgraded WWTPs showed a reduction of total sludge production (up to 45%) for the upgraded WWTP. The additional energy demand of the upgraded solution (+22.4 Wh/(PE d), PE: population equivalent) was partially balanced by the electric energy produced by combined heat and power unit installed in the upgraded WWTP (−18.08 Wh/(PE d)). The integrated assessment showed that the upgraded solution, although resulting in an increase of WWTP technical complexity, may contribute to environmental and economic advantages. The paper provides guidance in terms of which aspects need a more thorough evaluation when this upgrade is considered in real cases. [ABSTRACT FROM AUTHOR]

The legislative framework in force in Europe entails restrictive effluent standards for sensitive areas, and quite severe restrictions on the properties of residual sewage sludge, both for landfill disposal and for agricultural use. Several technologies and management strategies have been proposed and applied in wastewater treatment plants to minimise sludge production and contamination. However, their techno-economic and environmental performance has to be carefully evaluated. The ROUTES project, funded within the EU Seventh Framework programme, aims to find new routes for wastewater treatment and sludge management and thereby guide EU members in their future choices. Within this project, the authors have developed and applied a procedure for technoeconomic- environmental assessment of new wastewater and sludge processing lines in comparison to reference plants. The reference plants are model conventional plants that experience different types of problems and the new plants are modified plants in which different innovative technologies have been added to solve these problems. The procedure involves a rating of selected technical issues, estimates of operating costs and an assessment of environmental impacts from a life cycle perspective. This paper reports on the procedure and shows examples of results. [ABSTRACT FROM AUTHOR]

Abstract: A key issue in biological Waste Water Treatment Plants (WWTPs) operation is represented by the sludge management. Mechanical dewatering is a crucial stage for sludge volume reduction; though, being a costly operation, its optimization is required. We developed an original experimental methodology to evaluate the technical (dewatering efficiency) and financial (total treatment costs) performance of dewatering devices, which might be used as a DSS (Decision Support System) for WWTP managers. This tool was then applied to two real case studies for comparing, respectively, three industrial size centrifuges, and two different operation modes of the same machine (fixed installation vs. outsourcing service). In both the cases, the best option was identified, based jointly on economic and (site-specific) technical evaluations. [Copyright &y& Elsevier]

Highlights: [•] Failures in chemical phosphorus removal arise, occasionally, in some plants. [•] P release occurs based on settlers SRT, aerobic tanks DO, final effluent . [•] Unsuccessful control of these parameters can be corrected by post-precipitation. [•] Experimental outcomes could provide valuable information for practical applications. [ABSTRACT FROM AUTHOR]

Abstract: A major source of the wide presence of EDCs (Endocrine Disrupting Compounds) in water bodies is represented by direct/indirect discharge of sewage. Recent scientific literature reports data about their trace concentration in water, sediments and aquatic organisms, as well as removal efficiencies of different wastewater treatment schemes. Despite the availability of a huge amount of data, some doubts still persist due to the difficulty in evaluating synergistic effects of trace pollutants in complex matrices. In this paper, an integrated assessment procedure was used, based on chemical and biological analyses, in order to compare the performance of two full scale biological wastewater treatment plants (either equipped with conventional settling tanks or with an ultrafiltration membrane unit) and tertiary ozonation (pilot scale). Nonylphenol and bisphenol A were chosen as model EDCs, together with the parent compounds mono- and di-ethoxylated nonylphenol (quantified by means of GC–MS). Water estrogenic activity was evaluated by applying the human breast cancer MCF-7 based reporter gene assay. Process parameters (e.g., sludge age, temperature) and conventional pollutants (e.g., COD, suspended solids) were also measured during monitoring campaigns. Conventional activated sludge achieved satisfactory removal of both analytes and estrogenicity. A further reduction of biological activity was exerted by MBR (Membrane Biological Reactor) as well as ozonation; the latter contributed also to decrease EDC concentrations. [Copyright &y& Elsevier]

Removal potential of many EDCs by conventional WWTPs is recognized. Nevertheless, in order to reach very low concentrations, further treatment (e.g., chemical oxidation) might be required. In this work, two estrogen-like substances were considered: nonylphenol (NP) (and its parent compounds) and bisphenol A (BPA). The experimental work was conducted at Verona (Northern Italy) WWTP (370,000 p.e.): the effluent was submitted to ozonation in a pilot scale plant. Beside chemical and microbiological analyses, estrogenic activity measurements were also carried out by means of breast cancer MCF-7 cells transfected with the luminescence luciferase gene. Economic feasibility of tertiary ozonation is finally discussed. [ABSTRACT FROM AUTHOR]

Abstract: A non-conventional technique is proposed for the enclosure of either pure bacterial cultures or entire biocoenoses, for a possible utilization in the treatment of contaminated water. Biological components have been enclosed between polyester membranes coated by silica films consisting of: (a) SiO2 and nitrocellulose, (b) SiO2, ZnS crystals and nitrocellulose, (c) SiO2, TiO2 crystals and nitrocellulose, (d) SiO2, ZnS and TiO2 crystals and nitrocellulose. Morphological, structural and mechanical features of membranes were investigated by means of optical and electron microscopy, mercury porosimetry and wear resistance tests. Degradation kinetics have been finally studied by dipping the entrapped biomass into aqueous solutions of three different model organic compounds (α-d-glucose, ethyl alcohol and peptone). Results are very promising: in fact, no metabolic inhibition mechanisms of microorganisms have been evidenced. The porosity of the system allows mass transfer through the membranes, hence bacteria can grow and degrade pollutants. Besides, by this system, cells are constrained, avoiding they to spread across the retainment scaffold. [Copyright &y& Elsevier]

The metallurgical sector is one of the most emission- and energy-intensive industries. The possibility of using fossil carbon substitutes has been investigated to reduce the environmental impact of the steelmaking sector. Among others, biochar emerged as a promising fossil coal/coke substitute. We conducted a literature review on biochar use in the metallurgical sector and its potential environmental benefits. The possibility for biochar as a coal/coke substitute is influenced by the source of biochar production and the process within which it can be used. In general, it has been observed that substitution of biochar ranging from a minimum of 5% to a maximum of 50% (mostly around 20–25%) is possible without affecting, or in some cases improving, the process, in coke making, iron sintering, blast furnaces and electric furnaces application. In some studies, the potential CO2 reduction due to biochar use was estimated, ranging from 5% to about 50%. Despite there still being an area of further investigation, biochar appeared as a promising resource with a variety of uses in the metallurgical sector, contributing to the lowering of the environmental impact of the sector. [ABSTRACT FROM AUTHOR]

In order to achieve more effective and inclusive environmental and economic benefits, local industrial symbiosis programs need to be expanded to a regional scale. Research on regional industrial symbiosis (RIS) covers technical and non-technical aspects that have not yet been studied in detail. The goal of this paper is to identify the main topics and trends in this field of research. After proofreading of 956 Scopus-indexed documents extracted by keyword-search, 112 papers were selected as the core literature for the quantitative review. The sample represents a 22-year period (1997–2019), with over 63% of the articles published since 2015. The majority of case studies (64%) took place in Europe, China, the USA, and Australia. By applying social network analysis (SNA), keyword co-occurrence relations were investigated in the Gephi environment for distinguishing the main topics. The visualized network has a core-periphery structure. Six main subtopics were detected: industrial symbiosis and regional learning, waste minimization assessments, urban industrial symbiosis (UIS) and life cycle thinking, energy efficiency, operational carriers, and social aspects. Further document clustering demonstrated the division of papers in two groups representing differences in the geographical distribution of case studies, resources to be exchanged, and the organization of networks. The evolution of the sample in recent years was also examined, and its leading edges and weaker dimensions were identified. Additionally, a detailed content review is provided, which led to the mapping of main achievements and software tools under each subtopic. • Regional industrial symbiosis differs methodologically from other resource synergies. • The vast literature on this topic is reviewed based on social network analysis. • Six principal themes are detected in two separate clusters of papers. [ABSTRACT FROM AUTHOR]

Drinking water contamination by perfluoroalkyl and polyfluoroalkyl substances (PFASs) is an issue of relatively recent concern. The literature indicates that anion exchange resins and granular activated carbon (GAC) are suitable technologies for removing these compounds. While several laboratory-scale and pilot-scale experiments have been conducted to study activated carbon adsorption/desorption mechanisms of a number of PFASs, little data on full-scale plants are available. This work examines a real case of groundwater contamination by PFASs in an area of approximately 200 km2. The performance of the main drinking water treatment plant in the area (flowrate = 30,000 m3/d; 100,000 people served), which is equipped with GAC filters, was analysed. Approximately 17,000 analytical data points from a working period of five years were processed. Perfluorobutyric acid (PFBA) was the first compound to attain breakthrough, followed by perfluoropentanoic acid, perfluorohexanoic acid, perfluorobutanesulfonic acid, and perfluorooctanoic acid (PFOA). The adsorption capacity and treated bed volumes at complete breakthrough (saturation) were calculated, and ranged from 1.71 g/t and 7100 (PFBA) to 24.6 g/t and 50,900 (PFOA), with the total organic carbon concentration in the groundwater ranging from <0.1 to 0.5 mg/L. The overall adsorption capacity was approximately 40 g of total PFASs/t. The breakthrough behaviour of PFASs was correlated with the C F chain length, the type of hydrophilic head (either carboxyl or sulfonic), and the n -octanol/water partition coefficients logP and logD. The results corroborate the findings of previously published bench-scale and pilot-scale experiments. Unlabelled Image • The third largest PFASs groundwater contamination case worldwide was analysed. • A real GAC treatment plant was studied for 5 years (17,000 analytical data points). • PFASs achieved breakthrough in the order: PFBA, PFPeA, PFHxA, PFBS and PFOA. • Obtained adsorption capacity and BV range (PFBA-PFOA): 1.71–24.6(g/t); 7100–50,900. • A linear correlation between treated BV and logD was found. [ABSTRACT FROM AUTHOR]

A survey conducted in Italy revealed that less than 0.5% out of a sample of over 2,000 municipal wastewater treatment plants is equipped with an enhanced biological phosphorus removal process. Conditions promoting biological phosphorus removal have been investigated by monitoring three real plants equipped with, respectively: (A) simultaneous chemical precipitation; (B) enhanced biological removal powered by chemical precipitation; (C) tertiary chemical precipitation with evidence of phosphate accumulating bacteria. An anaerobic compartment revealed essential for the growth of these microorganisms, the readily degradable organic concentration in the influent playing a minor role. Mapping dissolved oxygen and oxidation-reduction potential in different compartments of plant (C) was carried out to understand the reasons why phosphate accumulating bacteria were found even in the absence of anaerobic reactor. Finally, the possibility to exploit the biological phosphorus removal in plant (C), by adjusting the aeration conditions, was explored and an economic analysis showed this to be a preferable approach with respect to the chemical removal of phosphorus. • The first Italian survey concerning EBPR application to urban WWTPs is presented. • Extensive and multi-level monitoring of three full-scale WWTPs was performed. • Factors promoting the presence of Polyphosphate Accumulating Bacteria were identified. • Economic evaluation of different alternatives for phosphorus removal was performed. • Experimental outcomes could provide valuable information for practical applications. [ABSTRACT FROM AUTHOR]

This work is aimed at assessing the effects of pretreated aqueous wastes stream-fed to a biological nutrient removal (BNR)- activated sludge plant. Aqueous wastes (mainly landfill leachate and liquid residues from chemical and pharmaceutical factories) are pretreated by means of a traditional coagulation-flocculation stage and subsequently sent to the BNR stage together with municipal wastewater. Pretreated aqueous wastes contribute up to about 75% of the influent load, in terms of chemical oxygen demand (COD; average concentration 23,000 mg=L). The resilience of the system, that is, the capacity to maintain high and stable performances despite sudden perturbations of the input conditions, was evaluated by interrupting the aqueous waste dosage and then progressively restoring the initial condition. The consequent variation of the influent load and composition caused a reduction of the biomass activity, which led to a decrease of the nitrogen removal efficiency (from 89% down to 73%). More than 30 days were required for restoring typical working conditions (in terms of influent load, process performance, and biomass activity), the sludge retention time (SRT) being 23 days. [ABSTRACT FROM AUTHOR]

A combination of thermophilic aerobic membrane reactor (TAMR) and conventional activated sludge (CAS) was studied by means of two pilot plants at semi-industrial scale in order to simulate the new configuration adopted in a full-scale facility for the treatment of high strength aqueous wastes. Aqueous wastes with high contents of organic pollutants were treated by means of the TAMR technology, progressively increasing the organic load (3–12 kg COD  m −3  d −1 ). A mixture of municipal wastewater and thermophilic permeate was fed to the CAS plant. The main results are the following: achievement of a high COD removal yield by both the TAMR (78%) and the CAS (85%) plants; ammonification of the organic nitrogen under thermophilic conditions and subsequent mesophilic nitrification; capacity of the downstream mesophilic process to complete the degradation of the organic matter partially obtained by the TAMR process and precipitation of phosphorus as vivianite and carbonatehydroxylapatite in the TAMR plant. [ABSTRACT FROM AUTHOR]

In the present work, the thermophilic aerobic membrane reactor technology was studied for the treatment of high strength aqueous wastes mainly containing dyes, surfactants and solvents. The thermophilic biomass resilience and the process stability under critical conditions (such as rapid rise of the mixed liquor pH, oxygen supply interruption, etc.) were also evaluated. The experimental work was carried out with the use of a pilot plant at semi-industrial scale, which was managed throughout for 14 months; the operation temperature was 49 °C and the organic loading rate was increased from 3 to 12 kgCOD m−3 d−1. Critical conditions, especially the interruption of oxygen supply, affected the pilot plant performance but did not cause a complete system break down. After the temporary reduction of process performance, also proven by the decrease in the oxygen consumption, the normal working conditions were restored. Moreover, the longer non-aerated phase involved a significant reduction (40%) of volatile suspended solids concentration in the biological reactor and the increase of 30% in foaming power; nevertheless, once the oxygen supply was reactivated, optimal conditions were rapidly restored. Therefore, the study showed the high resilience of the thermophilic biomass, which was able to recover full functionality after critical events. [ABSTRACT FROM AUTHOR]

The recovery of livestock manure, rich in nutrients, as fertilizer in agriculture, could pose the risk of an excessive load of nitrogen on the soil. Ammonia stripping is one of the available technologies for reducing the amount of nitrogen in the digestate obtained by the anaerobic digestion of manure. The study investigated the performance and energy consumption of a full-scale ammonia-stripping plant, equipped with a bubble reactor and working without the use of any alkaline reagent under semi-batch conditions. Stripping tests were conducted on the liquid fraction of the digestate, studying the current and optimized operative conditions of the plant. The main variables influencing the process were pH, temperature, airflow, and feed characteristics. In the experimental tests, the pH spontaneously increased to 10, without dosing basifying agents. Higher temperatures favoured the stripping process, the higher tested value being 68 °C. The airflow was kept equal to 15 Nm3 h−1 m−3digestate in the pre-stripping and to 60 Nm3 h−1 m−3digestate in the stripping reactors, during all tests. The energy requirement was completely satisfied by the CHP (combined heat and power) unit fed with the biogas produced by manure digestion. Results showed anaerobic digestion coupled with stripping to be a suitable solution for removing up to 81% of the ammonium with neither external energy input nor reagent dosage. [ABSTRACT FROM AUTHOR]

This paper is aimed at evaluating, from a techno-economic and environmental point of view, the performance of an existing wastewater treatment plant in which the traditional biological section is upgraded with an innovative Sequencing Batch Biofilter Granular Reactor. Two scenarios were simulated in order to model and assess the performances of conventional (CAS, Conventional Activated Sludge) and innovative solutions, based on mass balances, techno-economic evaluation and environmental assessment. The results showed that converting the activated sludge process into an SBBGR allows to achieve a drastic reduction in sludge production (up to 75% as volatile suspended solids). Furthermore, the secondary sedimentation and sludge stabilization units can be dismissed, reducing the area requirement (up to 50%). The technical assessment is mainly positive, with the electric energy consumption being the only critical item. The higher energy demand of the upgraded plant (about 25% more than the conventional treatment) is mainly associated with the recycle flow in the SBBGR system. Although the economic sustainability of the upgraded plant depends on local conditions, it can be considered to be likely favourable: sludge disposal and materials & reagents costs, together with the investment for plant reconstruction are those items that should be carefully evaluated before upgrading the CAS plant with SBBGR technology. The environmental assessment shows also mostly positive results, although it points to the increased phosphorus concentration in the effluent as a potentially critical issue and it highlights the electricity use and the increased nitrous oxide generation as other matters that need to be carefully checked in real case application. [ABSTRACT FROM AUTHOR]

Thermophilic biological fluidized bed reactors operating in aerobic/anoxic alternate conditions proved to be a feasible solution for sewage sludge minimization. However, to date, no data about energy released by thermophilic biota (ThBio) are available in literature. This work aims to estimate specific thermal energy released by ThBio highlighting the influence of daily anoxic conditions. A pilot-scale reactor (1 m3) was fed continuously with mesophilic sewage sludge and monitored for more than four months and a thermophysical model was applied to estimate thermal energy released by ThBio (k T,biota and k T,COD). Results suggested that the increase of daily anoxic time stimulated COD removal (92.7 ± 1.3 % vs. 81.3 ± 4.9 %, with 6 h and 0 h of daily anoxic time, respectively). The thermal energy released by ThBio was strictly dependent on anoxic conditions. In fact, increasing anoxic conditions from 0 h d−1 to 6 h d−1, k T,biota and k T,COD reduced from 1.8 ± 1.3 Mcal kg−1 VS kg−1 COD and 26.6 ± 13.7 Mcal kg−1 COD to 0.5 ± 0.1 Mcal kg−1 VS kg−1 COD and 15.6 ± 4.2 Mcal kg−1 COD , respectively. Although, biological mechanism responsible of this behaviour is not completely clear, this work can serve as reference for future studies about the optimization of conditions to maximize thermal energy release from ThBio during organic substance degradation alternate aerobic/anoxic, in view of subsequent energy recovery. [Display omitted] [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including phases of municipal wastewater treatment, model of developing integrated water demand model, and effect of anaerobic reject water on operational characteristics of wastewater treatment.

[Display omitted] Identify sustainable biological sewage sludge (BSS) management represents a current challenge. In this work, pre-thickened BSS taken from a large-scale urban wastewater treatment plant (WWTP) was fed continuously for about 9 months to a semi-industrial scale thermophilic biological fluidized bed reactor (TBFBR) operating in alternate conditions. The BSS treated in TBFBR was strongly reduced (89–92%) and the production was evaluated in 0.0007–0.0023 kg kg CODremoved −1 d−1 and 0.0004–0.0014 kg kg CODremoved −1 d−1 of TS and VS, respectively. The 92% of the P-PO 4 3- and P-org precipitated in inorganic form and accumulated in thermophilic biological sludge (TBS). In basic soils with chelating activity, phosphorus contained in TBS presented a higher bioavailability (84.0 ± 25.3%) with respect to untreated sludge. The analysis of four diverse scenarios highlighted that TBFBR located after pre-thickening could save 73–96% of operating costs with respect to current situation. [ABSTRACT FROM AUTHOR]

• Post-secondary settling can considerably impact wastewater disinfection efficiency. • A TSS settling model for post-secondary settling was developed and calibrated. • The rate expression of the double exponential disinfection model was analytically derived. • The CFD analysis brought new insights into the impact of settling on PAA disinfection. While the impact of suspended solids on chemical disinfection kinetics has been widely recognized, a detailed modeling framework for assessing their contribution on disinfection efficiency in municipal contact tanks is yet unavailable. In this paper, we conducted experimental and modeling studies to mechanistically describe the interplay between suspended solids (not removed by gravity settling in secondary clarifiers) and disinfection performance of an emerging disinfectant, peracetic acid, operated in a municipal contact tank. Specifically, we developed an integrated computational fluid dynamics (CFD) model to simultaneously predict the fate and transport of suspended solids, Escherichia coli and peracetic acid in a hypothetical reactor using an exposure-based (i.e., CT-based) inactivation rate expression. The integrated CFD model, calibrated against laboratory data, was used to gain insights on the vertical distribution and local PAA decay effect associated with solids settling and their impact on disinfectant decay and microbial inactivation. Results indicated that: (a) solids settling in contact tanks is a significant phenomenon that cannot be neglected, which can substantially impact disinfection efficiency under low flow conditions; (b) vertical solids distribution and stratification in contact tanks can strongly affect Escherichia coli inactivation by peracetic acid, as highlighted by the CFD modeling studies; (c) Escherichia coli settling is experimentally measurable, and strongly correlated with solids settling. These phenomena can be successfully integrated into a CFD model to obtain a comprehensive description of the PAA disinfection process in presence of changes in secondary effluent quality and flow, a situation typically encountered in municipal contact tanks operated in full scale wastewater treatment plants. [Display omitted] [ABSTRACT FROM AUTHOR]

• The effect of lockdown on NO 2 in London, Milan and Paris was assessed. • Data from 52 air quality control units were studied. • Comparison with 2017−2019 highlighted a high decrease in NO 2 due to low traffic. • Despite low traffic, NO 2 concentrations > 40 μg m−3 were registered for several days. • Rethink the vehicles, the city and its vehicular traffic are strongly suggested. Nitrogen dioxide (NO 2) can have harmful effects on human health and can act as a precursor for the formation of other air pollutants in urban environment such as secondary PM 2.5 and ozone. The lockdown measures for CoViD-19 allowed to simulate on a large scale the massive and prolonged reduction of road traffic (the main source for NO 2 in urban environment). This work aims to selectively assess the maximum impact that total traffic blocking measures can have on NO 2. For this reason, three megacities (London, Milan and Paris) were chosen which had similar characteristics in terms of climatic conditions, population, policies of urban traffic management and lockdown measures. 52 air quality control units have been used to compare data measured in lockdown and in the same periods of previous years, highlighting a significant decrease in NO 2 concentration due to traffic (London: 71.1 % - 80.8 %; Milan: 8.6 % - 42.4 %; Paris: 65.7 % - 79.8 %). In 2020 the contribution of traffic in London, Milan and Paris dropped to 3.3 ± 1.3 μg m−3, 6.1 ± 0.8 μg m−3, and 13.4 ± 1.5 μg m−3, respectively. Despite the significant reduction in the NO 2 concentration, in UT stations average NO 2 concentrations higher than 40 μg m−3 were registered for several days. In order to reduce the pollution, the limitation of road traffic could be not enough, but a vision also aimed at rethink the vehicles and their polluting effects should be developed. [ABSTRACT FROM AUTHOR]

The depletion of nitrogen and phosphorus represents a significant problem. Two real high strength wastewaters were treated by Thermophilic Aerobic Membrane Reactor (TAMR), an advanced biological process, obtaining significant removal of pollutants. Unlike the previous works, this paper does not focus on the optimization of the performance of the TAMR, but it studied the possible reuses of liquid (permeate) and solid (biological excess sludge) matrices to recover organic carbon, nitrogen and phosphorus and promote a circular economy model. The high nitrogen content of permeate can be exploited stripping ammonia with performances higher than 80% in best conditions to produce ammonium sulphate (useful as fertilizer). Moreover, the respiromeric tests demonstrated that permeate can be used in conventional active sludge systems as external source of organic carbon granting similar denitrification rate as methanol. In the sludge residue extracted from TAMR a significant presence of organic carbon and phosphorus (as hydroxyapatite) were revealed demonstrating the feasibility of recover this residue in land application. A preliminary management costs estimation showed that TAMR, coupled with a stripping and adsorption system to recover nutrients, is economically sustainable. Image 1 • Chemical oxygen demand (42–78%) and phosphorus (70–79%) were removed. • More than 80% of ammonia in permeate can be stripped to produce ammonium sulphate. • Permeate and methanol allow similar denitrification rate. • Hydroxyapatite was detected in sludge of thermophilic aerobic membrane reactor. • Preliminary management costs analysis highlights the economic feasibility. [ABSTRACT FROM AUTHOR]

• SARS-CoV-2 has been found in faeces and, in some cases, urine of infected people. • Wastewater and sewage sludge from infected area can contain SARS-CoV-2 RNA. • To date, virulence of SARS−COV-2 in sewage sludge has not been determined. • Wastewater monitoring could help to understand epidemic situation of urban areas. • Identify and sharing protocols for SARS-CoV-2 detection and analysis are fundamental. As for the SARS coronavirus in the 2003 epidemic, the presence of SARS-CoV-2 has been demonstrated in faeces and, in some cases, urine of infected people, as well as in wastewater. This paper proposes a critical review of the state of the art regarding studies on the presence of SARS-CoV-2 in wastewater and sewage sludge, the factors affecting its inactivation and the main proposed treatments. In-vitro tests demonstrated low resistance of SARS-CoV-2 to high temperature, while even significant changes in pH would not seem to determine the disappearance of the virus. In real wastewater and in sewage sludge, to date studies on the influence of the different parameters on the inactivation of SARS-CoV-2 are not available. Therefore, studies involving other HCoVs such as SARS-CoV and HCoV-229E have been also considered, in order to formulate a hypothesis regarding its behaviour in sewage and throughout the steps of biological treatments in WWTPs. Finally, SARS-CoV-2 in wastewater might track the epidemic trends: although being extremely promising, an effective and wide application of this approach requires a deeper knowledge of the amounts of viruses excreted through the faeces and the actual detectability of viral RNA in sewage. [ABSTRACT FROM AUTHOR]

Based on the rapid spread of the CoViD-2019, a lockdown was declared in the whole Northern Italy by the Government. The application of increasingly rigorous containment measures allowed to reduce the impact of the CoViD-2019 pandemic on the Italian National Health System but at the same time these restriction measures gave also the opportunity to assess the effect of anthropogenic activities on air pollutants in an unprecedented way. This paper aims to study the impact of the partial and total lockdown (PL and TL, respectively) on air quality in the Metropolitan City of Milan. As results, the severe limitation of people movements following the PL and the subsequent TL determined a significant reduction of pollutants concentration mainly due to vehicular traffic (PM 10 , PM 2.5 , BC, benzene, CO, and NO x). The lockdown led to an appreciable drop in SO 2 only in the city of Milan while it remained unchanged in the adjacent areas. Despite the significant decrease in NO 2 in the TL, the O 3 exhibited a significant increase, probably, due to the minor NO concentration. In Milan and SaA the increase was more accentuated, probably, due to the higher average concentrations of benzene in Milan than the adjacent areas that might have promoted the formation of O 3 in a more significant way. Unlabelled Image • The effect of lockdown on air quality in Milan was assessed. • The trends of 9 pollutants in meteorologically comparable periods were studied. • Lockdown determined a significant reduction of PM 10 , PM 2.5 , BC, benzene, CO and NO x. • SO 2 remained unchanged in the more peripheral areas. • Part of the ozone increase was probably due to the lower NO measured during lockdown. [ABSTRACT FROM AUTHOR]

Sludge recovery/disposal represents one of the most crucial aspects related to the management of wastewater treatment plants. The most widely diffused technology for the treatment of industrial and municipal wastewaters is the conventional activated sludge (CAS) process, which is characterized by a relatively high excess sludge production. Different technical solutions are proposed in the literature for sludge minimization and they can be applied either on wastewater line (WL) or sludge line (SL). This work is focused on different approaches based on the use of Thermophilic Aerobic Membrane Reactor (TAMR): this can be added to a CAS plant, and integrated to WL or SL, yielding a significant sludge reduction. The process performance was analysed in terms of volatile solids (VS) reduction and specific sludge production. The TAMR was tested both at full-scale and pilot-scale with different feeding substrates: industrial wastewater for the full-scale plant; industrial wastewater, sludge and a mix of these for the pilot-scale plants. The results obtained are: (i) good solids removal (38–90% and 40–50% in terms of VS for sludge and mix of industrial wastewater and sludge, respectively), (ii) low specific sludge production (0.01–0.09 kg VSS produced kg COD removed −1 for industrial wastewater and 0.014–0.069 kg VSS produced kg COD removed −1 for mix of industrial wastewater and sludge) and (iii) a significant reduction of sludge when CAS is improved with the TAMR technology. Image 1 • Different substrates were fed to Thermophilic Aerobic Membrane Reactor. • Upgrading of conventional activated sludge system were studied. • Up to 90% of volatile solids reduction was obtained. • Sludge production is one order of magnitude lower than other biological processes. [ABSTRACT FROM AUTHOR]

• A real laundry wastewater has been treated for the removal of surfactants. • A full-scale plant has been monitored for more than three months. • The yields of six possible combinations of processes have been evaluated. • TAMR has been able to perform an effective pre-treatment activity. • Costs analysis suggested that TAMR + NF was the optimal solution. Surfactants are considered emerging contaminants, that can represent a source of problems for environment and human health. This paper aims to quantify the effect of a thermophilic aerobic membrane reactor (TAMR), nanofiltration (NF) and adsorption on activated carbon (AC) for the removal of non-ionic surfactants (TAS) and anionic surfactants (MBAS) from a real laundry wastewater. This study included daily monitoring of a full-scale plant for more than three months. The results showed that the TAMR process has been able to withstand high stress conditions (sudden load peaks) and resist to a high concentration of surfactants, allowing it to perform an effective pre-treatment activity. Both in the case of the removal of TAS and of MBAS, the combination of processes made it possible to obtain higher removal yields. Evaluating the operating costs, the results suggested that TAMR + NF represented the optimal combination of processes for the removal of TAS and MBAS. The TAMR + NF + AC sequence allowed almost complete removal of TAS (> 95%) and high removal of MBAS (> 76%) but the costs per unit of mass removed were high. [ABSTRACT FROM AUTHOR]

A thermophilic aerobic membrane reactor (TAMR) treating high-strength COD liquid wastes was submitted to an integrated investigation, with the aim of characterizing the biomass and its rheological behaviour. These processes are still scarcely adopted, also because the knowledge of their biology as well as of the physical-chemical properties of the sludge needs to be improved. In this paper, samples of mixed liquor were taken from a TAMR and submitted to fluorescent in situ hybridization for the identification and quantification of main bacterial groups. Measurements were also targeted at flocs features, filamentous bacteria, and microfauna, in order to characterize the sludge. The studied rheological properties were selected as they influence significantly the performances of membrane bioreactors (MBR) and, in particular, of the TAMR systems that operate under thermophilic conditions (i.e., around 50°C) with high MLSS concentrations (up to 200 gTS L−1). The proper description of the rheological behaviour of sludge represents a useful and fundamental aspect that allows characterizing the hydrodynamics of sludge suspension devoted to the optimization of the related processes. Therefore, in this study, the effects on the sludge rheology produced by the biomass concentration, pH, temperature, and aeration were analysed. [ABSTRACT FROM AUTHOR]

This paper presents the results of a broad-scale survey of resource recovery implementation in Italian wastewater treatment plants (WWTPs). To the best of our knowledge, this is the first survey comprising a large number of WWTPs done in Europe: more than 600 plants were investigated, representing a treated load of around 20 million population equivalent (≈25% of the total in Italy). Conventional and innovative options for both material and energy recovery along the water and sludge line were surveyed, in order to i) offer a real and complete picture of the current state of resource recovery in WWTPs, and ii) underline key aspects and potential areas for improvements, as a baseline for future developments in the direction of more sustainable plants. Survey outcomes showed that resource recovery is just in its infancy in sewage treatment: only 40% of plants perform at least one option for material/energy recovery. The action most often implemented is recovery of material from surplus sludge for agricultural purposes and the internal reuse of treated effluent as water for various types of plant maintenance. The production of energy from biogas also occurs frequently but only in large plants. On the other hand, some well-known options, such as external reuse of treated effluent or nutrients recovery, were implemented only in a minority of plants: this is likely due to limitations resulting either from strict regulation or difficulty placing recovered products on the market. In conclusion, an overall explanation of these driving forces within the system is explored. [ABSTRACT FROM AUTHOR]

The increase of sewage sludge production together with the high treatment and disposal costs in the last years has pushed to study different solutions aimed at sludge minimization. In this paper, the thermophilic membrane technology was evaluated as an alternative for municipal sewage sludge reduction. The experimentation (carried out by means of a pilot scale plant, 1 m 3 volume) was divided into two steps: the first one was aimed at confirming the results obtained in a previous research focused on industrial sludge treatment; the second step was devoted to define the best process conditions (in particular the optimization of the aeration phases) and to the chemical permeate characterization. The results of the experiments highlight that the hydraulic retention time (HRT) and aeration conditions play a crucial role on the overall process performance. The volatile suspended solids removal efficiency was greater than 80% under the following conditions: HRT even lower than 15 d; 2 h of aeration - 6 h of non aeration cycles; and organic loading rate of 2.0 kgCOD m −3 d −1 . The permeate showed a good biodegradability under mesophilic conditions thus being treatable by means of conventional biological processes. Moreover, ammonia (the permeate presenting high concentrations) could be recovered as a fertilizer (stripping and subsequent washing of the exhausted gas is an established technique). Finally, the ammonia-free permeate can be valorised as a carbon source in denitrification processes. [ABSTRACT FROM AUTHOR]

Piggery slaughterhouse wastewater poses serious issues in terms of disposal feasibility and environmental impact, due to its huge organic load and variability. It is commonly treated by means of activated sludge processes, whose performance, in case of municipal wastewater, can be monitored by means of specific analyses, such as Sludge Biotic Index (SBI), Sludge Index (SI) and floc and filamentous bacteria observation. Therefore, this paper was aimed at assessing the applicability of these techniques to piggery slaughterhouse sewage. A plant located in Northern Italy was monitored for 1 year. Physical, chemical and operation parameters were measured; the activated sludge community (ciliates, flagellates, amoebae and small metazoa) was analysed for calculating SBI and SI. Floc and filamentous bacteria were examined and described accordingly with internationally adopted criteria. The results showed the full applicability of the studied techniques for optimizing the operation of a piggery slaughterhouse wastewater treatment plant. [ABSTRACT FROM AUTHOR]

A chemical and bio-analytical protocol is proposed as a holistic monitoring framework for the assessment of WWTPs (Wastewater Treatment Plants) performance. This combination of tests consists of: i) an analysis of emerging contaminants, to be added to the established physico–chemical parameters in order to understand the causes of (new) pollution phenomena and ii) some of the bio-analytical tools most widely applied in the field of wastewater research, which provide information on groups of chemicals with a common mode of toxic action (baseline toxicity, estrogenicity and mutagenicity/genotoxicity, selected as the most representative for human health). The negative effects of the discharge can thus be highlighted directly and used to assess the global environmental impact of WWTPs. As a validation, this multi-tiered approach was applied to a full-scale WWTP (150,000 p.e.), where different measurements were carried out: EDCs (Endocrine Disrupting Compounds) detection; algal growth inhibition, bioluminescence inhibition and acute toxicity test (for baseline toxicity); an E-Screen-like assay (for estrogenic activity); Ames, Allium cepa and Comet tests (for mutagenic/genotoxic activity). As a result, the WWTP showed good performance for all these issues, displaying its ability to enhance effluent quality, except for residual mutagenic behaviour, probably due to the by-products generated by the tertiary ozonation. [ABSTRACT FROM AUTHOR]

Several decision support systems have been developed in recent years, aimed at judging environmental technologies under the lens of a multi-criteria analysis. This has also been applied in the field of wastewater treatment, where different factors (techno-economic-environmental) are inherent to the process and have to be balanced. The aim of this work is to calculate the damage on human health as a key factor for the evaluation of different wastewater treatment processes. The damage due to emissions into both water and air was taken into account. Indeed, the benefits related to the improved effluent quality after treatment could be counteracted by the negative effects when computing atmospheric emissions related to energy requirement. While a set of specific cost factors was applied for air pollution, a highly innovative perspective was adopted in the case of water pollution: several biological assays were used to weight waterborne diseases. Their application in the framework of a decision making process represents a novel approach in the wastewater domain. In short, we found that the economic equivalent of the impact on human health is remarkably affected by the selected treatment train, ranging from ≈2 €/PE/y for advanced systems up to ≈3 €/PE/y for conventional activated sludge plants. In particular, the most advisable schemes consist of an activated sludge plant integrated with either i) activated carbon and sand filtration or ii) sand filtration and ozonation. Finally, the applicability of the proposed procedure is also discussed and compared with the conventional life cycle assessment (LCA) approach, and the main difference is pointed out: for the former, biological assays and related diseases are used for endpoint calculation while the latter is based on the effect of each single compound. [ABSTRACT FROM AUTHOR]

The management of sewage sludge is becoming a more and more important issue, both at national and international level, in particular due to the uncertain recovery/disposal future options. Therefore, it is clear that the development of new technologies that can mitigate the problem at the source by reducing sludge production is necessary, such as the European Directive 2008/98/EC prescribes. This work shows the results obtained with a thermophilic membrane reactor, for processing a biological sludge derived from a wastewater treatment plant (WWTP) that treats urban and industrial wastewater. Sewage sludge was treated in a thermophilic membrane reactor (TMR), at pilot-scale (1 m 3 volume), with alternate aeration cycles. The experimentation was divided into two phases: a “startup phase” during which, starting with a psychrophilic/mesophilic biomass, thermophilic conditions were progressively reached, while feeding a highly biodegradable substrate; the obtained thermophilic biomass was then used, in the “regime phase”, to digest biological sludge which was fed to the plant. Good removal yields were observed: 64% and 57% for volatile solids (VS) and total COD (COD tot ), respectively, with an average hydraulic retention time (HRT) equal to 20 d, an organic loading rate (OLR) of about 1.4–1.8 kg COD m −3 d −1 and aeration/non aeration cycles alternated every 4 h. [ABSTRACT FROM AUTHOR]

Minimizing the biological sewage sludge (BSS) produced by wastewater treatment plants (WWTPs) represents an increasingly difficult challenge. With this goal, tests on a semi-full scale Thermophilic Alternate Membrane Biological Reactor (ThAlMBR) were carried out for 12 months. ThAlMBR was applied both on thickened (TBSS) and digested biological sewage sludge (DBSS) with alternating aeration conditions, and emerged: (i) high COD removal yields (up to 90%), (ii) a low specific sludge production (0.02–0.05 kgVS produced/kgCODremoved), (iii) the possibility of recovery the aqueous carbon residue (permeate) in denitrification processes, replacing purchased external carbon sources. Based on the respirometric tests, an excellent biological treatability of the permeate by the mesophilic biomass was observed and the denitrification kinetics reached with the diluted permeate ((4.0 mgN-NO3−/(gVSS h)) were found comparable to those of methanol (4.4 mgN-NO3−/(gVSS h)). Moreover, thanks to the similar results obtained on TBSS and DBSS, ThAlMBR proved to be compatible with diverse sludge line points, ensuring in both cases an important sludge minimization. [ABSTRACT FROM AUTHOR]

[Display omitted] • A literature review on integrated MBR modelling and control is presented. • The use of integrated MBR models should be more encouraged. • A new framework was proposed to pursue good practice for MBR modelling. • Integrated MBR modelling applications to real case studies is needed. Integrated Membrane Bioreactor (MBR) models, combination of biological and physical models, have been representing powerful tools for the accomplishment of high environmental sustainability. This paper, produced by the International Water Association (IWA) Task Group on Membrane Modelling and Control, reviews the state-of-the-art, identifying gaps for future researches, and proposes a new integrated MBR modelling framework. In particular, the framework aims to guide researchers and managers in pursuing good performances of MBRs in terms of effluent quality, operating costs (such as membrane fouling, energy consumption due to aeration) and mitigation of greenhouse gas emissions. [ABSTRACT FROM AUTHOR]

The recent trend of turning wastewater treatment plants (WWTPs) into energy self-sufficient resource recovery facilities has led to a constant search for solutions that fit into that concept. One of them is chemically enhanced primary treatment (CEPT), which provides an opportunity to increase biogas production and to significantly reduce the amount of sludge for final disposal. Laboratory, pilot, and full-scale trials were conducted for the coagulation and sedimentation of primary sludge (PS) with iron sulphate (PIX). Energy and economic balance calculations were conducted based on the obtained results. Experimental trials indicated that CEPT contributed to an increase in biogas production by 21% and to a decrease in sludge volume for final disposal by 12% weight. Furthermore, the application of CEPT may lead to a decreased energy demand for aeration by 8%. The removal of nitrogen in an autotrophic manner in the side stream leads to a further reduction in energy consumption in WWTP (up to 20%). In consequence, the modeling results showed that it would be possible to increase the energy self-sufficiency for WWTP up to 93% if CEPT is applied or even higher (up to 96%) if, additionally, nitrogen removal in the side stream is implemented. It was concluded that CEPT would reduce the operating cost by over 650,000 EUR/year for WWTP at 1,000,000 people equivalent, with a municipal wastewater input of 105,000 m3/d. [ABSTRACT FROM AUTHOR]